The present invention relates to a device for rolling elongated elements, particularly for producing tobacco items.
The present invention is particularly advantageous for producing filter-tipped cigarettes, to which the following description refers purely by way of example.
In the manufacture of tobacco items in general, and cigarettes in particular, the items are rolled about their axis for various reasons. For example, filter-tipped cigarettes are rolled as part of laser perforating processes for producing ventilated cigarettes; or groups, each comprising two coaxial cigarette portions separated by a double filter, are rolled for connecting the cigarette portions to the double filter by means of an adhesive strip which is rolled about the filter and the adjacent ends of the cigarette portions.
For the sake of simplicity, specific reference will be made in the following description to the second of the above applications.
Known rolling devices for producing double filter-tipped cigarettes comprise a conveyor roller with a number of seats equally spaced about the outer surface of the roller and for receiving and retaining respective groups; and, normally, also a fixed plate facing an outer peripheral portion of the roller and defining with it a rolling channel of a width approximately equal to but no larger than the diameter of the cigarette portions and the double filter. The conveyor roller is rotated about its axis at constant speed to feed the groups and respective adhesive strips--connected in projecting manner to the groups--to the inlet of the channel at a first given speed, and to feed the groups along the channel at a second speed equal to half the first speed.
The rolling channel inlet is normally provided with a rolling initiating device normally defined by a fixed tooth which, as described and illustrated, for example, in U.S. Pat. No. 3,527,234, extends partly inside the channel and, as the groups arrive, cooperates with them by friction to withdraw them from the respective seats on the conveyor roller and rotate them backwards about their respective axes.
On known rolling devices of the above type, each group encounters the initiating tooth at full speed, and is subjected to extremely sharp (theoretically infinite) deceleration which, regardless of impact speed, can only be absorbed by elastic deformation of the group itself. Since, for output speeds over and above a given limit, impact is such as to result in irreparable damage to the group, the above fixed initiating tooth design obviously limits the output capacity of the filter assembly machine.
To at least partly overcome the above drawback, U.S. Pat. No. 4,825,882 relates to a rolling device wherein the fixed initiating tooth described above is replaced by a succession of initiating teeth fitted to a roller and moving with it at a speed equal to half the traveling speed of the groups.
Though this provides for increasing the output speed of the filter assembly machine, it fails to eliminate the extremely sharp fall in the traveling speed of the groups entering the rolling channel.